Wide-angle image lens with high resolution and short overall length

Abstract

A wide-angle image lens, in the order from the object side to the image side thereof, includes a first lens, a second lens, a third lens, a fourth lens and an image plane. The image lens satisfies the following formulas: D/TTL>0.45; CT4/ET4<2.11; Z/Y>0.06; wherein D is the maximum image diameter of the image plane; TTL is a total length of the wide-angle image lens; CT4 is a distance along an optical axis from the seventh surface to the eighth surface; ET4 is a distance along the optical axis from an outmost edge of the seventh surface to an outmost edge of the eighth surface; Z is a distance from a central point of the fifth surface to an outmost edge of the sixth surface along the optical axis; Y is a distance from the outmost edge of the sixth surface to the optical axis.

What is claimed is: 
     
       1. A wide-angle image lens, in the order from the object side to the image side thereof, comprising:
 a first lens having positive refraction power and comprising a first surface facing the object side and a second surface facing the image side; 
 a second lens having positive refraction power and comprising a third surface facing the object side and a fourth surface facing the image side; 
 a third lens having negative refraction power and comprising a fifth surface facing the object side and a sixth surface facing the image side; 
 a fourth lens having positive refraction power and comprising a seventh surface facing the object side and an eighth surface facing the image side; and 
 an image plane; 
 wherein the image lens satisfies the following formulas:
     D/TTL> 0.45; 
     CT 4 /ET 4<2.11; 
     Z/Y> 0.06; 
 
 wherein D is the maximum image diameter of the image plane; TTL is a total length of the wide-angle image lens; CT4 is a distance along an optical axis of the wide-angle image lens from the seventh surface to the eighth surface; ET4 is a distance in a direction parallel to the optical axis of the wide-angle image lens from an outmost edge of the seventh surface to an outmost edge of the eighth surface; Z is a distance from a central point of the fifth surface to an outmost edge of the sixth surface along the optical axis; Y is a distance from the outmost edge of the sixth surface to the optical axis along a direction perpendicular to the optical axis; 
 wherein the wide-angle image lens further satisfies the formulas:
   0< R 11/ F 1<0.24 and 0< R 12/ F 1<0.26; 
 
 wherein R11 is a curvature radius of the first surface; R12 is a curvature radius of the second surface; F1 is a focal length of the first lens. 
 
     
     
       2. The wide-angle image lens as claimed in  claim 1 , wherein the wide-angle image lens further satisfies the formulas:
   −0.80< R 21/ F 2<0 and −0.4< R 22 /F 2<0;
 
 wherein R21 is a curvature radius of the third surface; R22 is a curvature radius of the fourth surface; F2 is a focal length of the second lens. 
 
     
     
       3. The wide-angle image lens as claimed in  claim 1 , wherein the wide-angle image lens further satisfies the formulas:
   0< R 41 /F 4<0.59 and 0< R 42/ F 4<4.39; 
 wherein R41 is a curvature radius of the seventh surface; R42 is a curvature radius of the eighth surface; F4 is a focal length of the fourth lens. 
 
     
     
       4. The wide-angle image lens as claimed in  claim 1 , wherein the wide-angle image lens further satisfies the formulas:
     Vd 1>53,  Vd 2>53,  Vd 3>53, and  Vd 4>53; 
 wherein Vd1 is the Abbe number of the first lens; Vd2 is the Abbe number of the second lens; Vd3 is the Abbe number of the third lens; and Vd4 is the Abbe number of the fourth lens. 
 
     
     
       5. The wide-angle image lens as claimed in  claim 1 , wherein the first, second, third, fourth, fifth, sixth, seventh, and eighth surfaces are aspherical surfaces. 
     
     
       6. The wide-angle image lens as claimed in  claim 1 , wherein the first surface is a convex surface facing the object side, the second surface is a concave surface facing the image side, the third surface is a concave surface facing the object side, the fourth surface is a convex surface facing the image side, the fifth surface is a concave surface facing the object side, the sixth surface is a convex surface facing the image side, the seven surface is a convex surface facing the object side, and the eighth surface is a convex surface facing the image side. 
     
     
       7. The wide-angle image lens as claimed in  claim 1 , further comprising an aperture stop, wherein the aperture stop is positioned between the first lens and the second lens. 
     
     
       8. The wide-angle image lens as claimed in  claim 1 , further comprising an IR-cut filter, wherein the IR-cut filter is positioned between the fourth lens and the image plane. 
     
     
       9. The wide-angle image lens as claimed in  claim 8 , further comprising a protective glass, wherein the protective glass is positioned between the IR-cut filter and the image plane. 
     
     
       10. A wide-angle image lens, in the order from the object side to the image side thereof, comprising:
 a first lens having positive refraction power and comprising a first surface facing the object side and a second surface facing the image side; 
 a second lens having positive refraction power and comprising a third surface facing the object side and a fourth surface facing the image side; 
 a third lens having negative refraction power and comprising a fifth surface facing the object side and a sixth surface facing the image side; 
 a fourth lens having positive refraction power and comprising a seventh surface facing the object side and an eighth surface facing the image side; and 
 an image plane; 
 wherein the image lens satisfies the following formulas:
     D/TTL> 0.45; 
     CT 4 /ET 4<2.11; 
     Z/Y> 0.06; 
 
 wherein D is the maximum image diameter of the image plane; TTL is a total length of the wide-angle image lens; CT4 is a distance along an optical axis of the wide-angle image lens from the seventh surface to the eighth surface; ET4 is a distance in a direction parallel to the optical axis of the wide-angle image lens from an outmost edge of the seventh surface to an outmost edge of the eighth surface; Z is a distance from a central point of the fifth surface to an outmost edge of the sixth surface along the optical axis; Y is a distance from the outmost edge of the sixth surface to the optical axis along a direction perpendicular to the optical axis; 
 wherein the wide-angle image lens further satisfies the formulas:
   0<| R 11 /F 1|<| R 32 /F 3|<| R 22 /F 2|<| R 41 /F 4|; 
 
 wherein R11 is a curvature radius of the first surface of the first lens; F1 is a focal length of the first lens; R32 is a curvature radius of the sixth surface; F3 is a focal length of the third lens; 
 R22 is a curvature radius of the fourth surface; F2 is a focal length of the second lens; R41 a curvature radius of the seventh surface; F4 is a focal length of the fourth lens. 
 
     
     
       11. The wide-angle image lens as claimed in  claim 10 , wherein the wide-angle image lens further satisfies the formulas:
   | R 42 /F 4|>| R 41 /F 4|>0; 
 wherein R42 is a curvature radius of the eighth surface of the fourth lens. 
 
     
     
       12. A wide-angle image lens, in the order from the object side to the image side thereof, comprising:
 a first lens having positive refraction power and comprising a first surface facing the object side and a second surface facing the image side; 
 a second lens having positive refraction power and comprising a third surface facing the object side and a fourth surface facing the image side; 
 a third lens having negative refraction power and comprising a fifth surface facing the object side and a sixth surface facing the image side; 
 a fourth lens having positive refraction power and comprising a seventh surface facing the object side and an eighth surface facing the image side; and 
 an image plane; 
 wherein the image lens satisfies the following formulas:
     D/TTL> 0.45; 
     CT 4 /ET 4<2.11; 
     Z/Y> 0.06; 
 
 wherein D is the maximum image diameter of the image plane; TTL is a total length of the wide-angle image lens; CT4 is a distance along an optical axis of the wide-angle image lens from the seventh surface to the eighth surface; ET4 is a distance in a direction parallel to the optical axis of the wide-angle image lens from an outmost edge of the seventh surface to an outmost edge of the eighth surface; Z is a distance from a central point of the fifth surface to an outmost edge of the sixth surface along the optical axis; Y is a distance from the outmost edge of the sixth surface to the optical axis along a direction perpendicular to the optical axis; 
 wherein the wide-angle image lens further satisfies the formulas:
   0< R 31/ F 3<0.2 and 0< R 32/ F 3<0.28; 
 
 wherein R31 is a curvature radius of the fifth surface; R32 is a curvature radius of the sixth surface; F3 is a focal length of the third lens.